Hitherto, a surveillance camera installed on walls or ceilings of facilities is known. Such surveillance camera includes a dome cover for containing and protecting a lens. The dome cover is typically made of transparent resin. The dome cover includes a semi-spherical dome portion which has an opening and a flange portion which is provided with the peripheral edge of the opening. The lens of the surveillance camera rotates in a pan direction or in a tilt direction in a state of being contained in the dome cover. Shooting of surveillance video is carried out through the transparent dome cover. The dome cover is required to have an optically high performance. For example, the dome cover is required to have a performance to provide a high-quality, high-resolution camera image shot therethrough. A dome-type camera as described above is disclosed in JP-A-2005-300659 (pages 4-6, FIG. 2).
The dome cover as described above is manufactured, for example, by injection molding. A cavity which has a shape corresponding to the shape of the dome cover is formed between an upper mold and a lower mold of a metal mold used for the injection molding. The metal mold for injection molding in the prior art has a gate port for injecting resin at a position corresponding to the flange portion of the dome cover so as to prevent a gate trace from being left on the dome portion of the molded dome cover. For example, the gate port is provided with a lateral side of the cavity (a circumference of the substantially circular cavity in plan view). Then, heated and melt resin is injected into the cavity through the gate port of the injection molding die, and the resin is cooled and cured. In this manner, the dome cover is manufactured by the injection molding. Such injection molding die is disclosed, for example, in JP-A-2003-285351 (pages 3-6, FIG. 2).
However, according to the method of manufacturing the dome cover in the prior art, the resin is injected through the gate port provided with the lateral side of the cavity. Therefore, the resin injected from the lateral side of the cavity (one of the circumferences of the substantially circular cavity in plan view) flows around to the center of the cavity (which corresponds to a zenithal portion of the dome cover), and then flows toward an exit portion of the other circumference of the cavity. When the resin flows in the cavity as described above, the flow of the resin is not uniform near the gate port and the exit portion, and the pressure and the temperature of resin in the cavity varies. Therefore, the dome cover manufactured in the method in the prior art, molding irregularity occurs at portions corresponding to the gate port and the exit portion, and hence optical irregularities (lowering of the quality or the resolution of the camera image) may occur.